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Diffstat (limited to 'arch/x86/kvm/mmu/mmu.c')
-rw-r--r--arch/x86/kvm/mmu/mmu.c47
1 files changed, 23 insertions, 24 deletions
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index de73d986a282..e1d011c67cc6 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3589,7 +3589,9 @@ void kvm_mmu_free_roots(struct kvm *kvm, struct kvm_mmu *mmu,
&invalid_list);
if (free_active_root) {
- if (root_to_sp(mmu->root.hpa)) {
+ if (kvm_mmu_is_dummy_root(mmu->root.hpa)) {
+ /* Nothing to cleanup for dummy roots. */
+ } else if (root_to_sp(mmu->root.hpa)) {
mmu_free_root_page(kvm, &mmu->root.hpa, &invalid_list);
} else if (mmu->pae_root) {
for (i = 0; i < 4; ++i) {
@@ -3637,19 +3639,6 @@ void kvm_mmu_free_guest_mode_roots(struct kvm *kvm, struct kvm_mmu *mmu)
}
EXPORT_SYMBOL_GPL(kvm_mmu_free_guest_mode_roots);
-
-static int mmu_check_root(struct kvm_vcpu *vcpu, gfn_t root_gfn)
-{
- int ret = 0;
-
- if (!kvm_vcpu_is_visible_gfn(vcpu, root_gfn)) {
- kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu);
- ret = 1;
- }
-
- return ret;
-}
-
static hpa_t mmu_alloc_root(struct kvm_vcpu *vcpu, gfn_t gfn, int quadrant,
u8 level)
{
@@ -3787,8 +3776,10 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
root_pgd = kvm_mmu_get_guest_pgd(vcpu, mmu);
root_gfn = root_pgd >> PAGE_SHIFT;
- if (mmu_check_root(vcpu, root_gfn))
- return 1;
+ if (!kvm_vcpu_is_visible_gfn(vcpu, root_gfn)) {
+ mmu->root.hpa = kvm_mmu_get_dummy_root();
+ return 0;
+ }
/*
* On SVM, reading PDPTRs might access guest memory, which might fault
@@ -3800,8 +3791,8 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
if (!(pdptrs[i] & PT_PRESENT_MASK))
continue;
- if (mmu_check_root(vcpu, pdptrs[i] >> PAGE_SHIFT))
- return 1;
+ if (!kvm_vcpu_is_visible_gfn(vcpu, pdptrs[i] >> PAGE_SHIFT))
+ pdptrs[i] = 0;
}
}
@@ -3968,7 +3959,7 @@ static bool is_unsync_root(hpa_t root)
{
struct kvm_mmu_page *sp;
- if (!VALID_PAGE(root))
+ if (!VALID_PAGE(root) || kvm_mmu_is_dummy_root(root))
return false;
/*
@@ -4374,6 +4365,10 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault
{
int r;
+ /* Dummy roots are used only for shadowing bad guest roots. */
+ if (WARN_ON_ONCE(kvm_mmu_is_dummy_root(vcpu->arch.mmu->root.hpa)))
+ return RET_PF_RETRY;
+
if (page_fault_handle_page_track(vcpu, fault))
return RET_PF_EMULATE;
@@ -4609,9 +4604,8 @@ static bool fast_pgd_switch(struct kvm *kvm, struct kvm_mmu *mmu,
gpa_t new_pgd, union kvm_mmu_page_role new_role)
{
/*
- * For now, limit the caching to 64-bit hosts+VMs in order to avoid
- * having to deal with PDPTEs. We may add support for 32-bit hosts/VMs
- * later if necessary.
+ * Limit reuse to 64-bit hosts+VMs without "special" roots in order to
+ * avoid having to deal with PDPTEs and other complexities.
*/
if (VALID_PAGE(mmu->root.hpa) && !root_to_sp(mmu->root.hpa))
kvm_mmu_free_roots(kvm, mmu, KVM_MMU_ROOT_CURRENT);
@@ -5510,14 +5504,19 @@ static bool is_obsolete_root(struct kvm *kvm, hpa_t root_hpa)
/*
* When freeing obsolete roots, treat roots as obsolete if they don't
- * have an associated shadow page. This does mean KVM will get false
+ * have an associated shadow page, as it's impossible to determine if
+ * such roots are fresh or stale. This does mean KVM will get false
* positives and free roots that don't strictly need to be freed, but
* such false positives are relatively rare:
*
- * (a) only PAE paging and nested NPT has roots without shadow pages
+ * (a) only PAE paging and nested NPT have roots without shadow pages
+ * (or any shadow paging flavor with a dummy root, see note below)
* (b) remote reloads due to a memslot update obsoletes _all_ roots
* (c) KVM doesn't track previous roots for PAE paging, and the guest
* is unlikely to zap an in-use PGD.
+ *
+ * Note! Dummy roots are unique in that they are obsoleted by memslot
+ * _creation_! See also FNAME(fetch).
*/
sp = root_to_sp(root_hpa);
return !sp || is_obsolete_sp(kvm, sp);